Dental caries, i.e., tooth decay, is a leading cause of tooth damage in humans. Dental caries begins with lesions of so-called “white spots”, which are demineralized areas below the surface of intact dental enamel. Such subsurface lesions are formed before a cavity is detectable. If unchecked, surface enamel above a subsurface lesion eventually collapses, leading to cavitations and subsequent loss of tooth structure.
The primary component of the enamel and dentin in teeth is calcium phosphate in the form of calcium hydroxyapatite. This material is highly insoluble at normal oral pHs. However, calcium phosphate salts are more soluble in acidic media, and they are subjected to acids produced from the glycolysis of sugars by the action of various oral bacteria. Therefore, the acids cause carious lesions that form in teeth.
Although it is desirable to prevent caries from spreading, it is also desirable to restore the carious tooth to its original state. Restoration of a carious tooth to its original state involves the process of remineralization. The object of remineralization is to deposit hydroxyapatite in the carious lesion such that the dental enamel incorporates the hydroxyapatite into its structure at the point of lesion. Thus, remineralization not only prevents further tooth decay but also restores the tooth to its original state.
Saliva is supersaturated with respect to calcium and phosphate ions. Saliva therefore helps protect teeth against demineralization and can slowly remineralize teeth that have become demineralized by acids. It is also well known that the presence of fluoride ions can enhance the natural remineralization process and this is one of the accepted mechanisms by which fluoride toothpastes and rinses protect against caries. However, the modest levels of calcium and phosphate in saliva limit the efficacy of fluoride containing toothpastes and rinses to remineralize teeth. Therefore, it is highly desirable to increase the available concentration of calcium and phosphate ions in the oral cavity to speed up the remineralization process. To do so, one must taking into account of calcium phosphate's low solubility at the pH of saliva, and that calcium ions must be prevented from reacting with the phosphate ions or fluoride ions until immediately before use, so that the ions would not precipitate prematurely before reach oral cavity.
A variety of methods and compositions have been described in the prior art to attempt to cure the deminineralization problem. Examples are U.S. Pat. Nos. 5,037,639; 5,268,167; 5,437,857; 5,427,768; and 5,460,803 (all to Tung), teach the use of amorphous calcium compounds such as amorphous calcium phosphate (ACP), amorphous calcium phosphate fluoride (ACPF) and amorphous calcium carbonate phosphate (ACCP) for use in remineralizing teeth. These amorphous compounds or solutions which form the amorphous compounds when applied either onto or into dental tissue prevent and/or repair dental weaknesses such as dental caries, exposed roots and dentin sensitivity. The compounds are claimed to have high solubilities, fast formation rates and fast conversion rates (to apatite). In the Tung patents, remineralization is accomplished by bringing the amorphous compound into contact with the dental tissue. This can be done directly, i.e., putting an amorphous compound directly on the tooth, or indirectly through a carrier, i.e., incorporating the amorphous compound in a carrier such as a gel, a chewing gum, or a toothpaste and applying the carrier to the dental tissue. Once contact is established with the tooth, the amorphous calcium phosphate compounds will recrystallize to the less soluble apatite form in the lesion and reform the tooth. However, under conditions where amorphous calcium phosphate compounds are stable, the quantity of calcium and phosphate released is relatively low and, therefore, remineralization is slower than desirable.
The aforementioned patents to Tung teach the use of two-part solutions wherein a first part contains phosphate salt(s) and a second part contains calcium salts(s), wherein either the first part or the second part further contains carbonate salt(s). In addition, the Tung patents teach solutions formed by dissolving in water a solid powder containing calcium salt(s). These solutions are salt(s) and carbonate salt(s). These solutions are then applied to dental tissue. The Tung patents further teach the use of non-carbonated solid powders containing mixtures of calcium salts and phosphate salts which can be applied directly to the tooth or dispersed in gel, chewing gum, or other non-aqueous medium such as toothpaste which is placed in contact with the tooth. The patents teach that these powders are easily dissolved in saliva and then reprecipitated as an amorphous calcium phosphate compound. However, the Tung patents do not disclose the pHs of aqueous solutions formed from the non-carbonated solid powders.
Another example is U.S. Pat. No. 5,571,502 to Winston et al. is directed to one-part, non-aqueous products and methods of using same to remineralize subsurface lesions, wherein the products contain at least one water-soluble calcium salt; at least one water-soluble phosphate salt; either a stabilizer or a hydrophilic, non-aqueous, water-soluble vehicle; and, optionally, at least one water-soluble fluoride salt. When the components are mixed with water or saliva to form an aqueous mixed solution, the solution has a pH of from about 4.5 to about 10.0.
Another example is U.S. Pat. No. 6,159,449 to Winston et al., is directed to two-parts, simultaneously releasable dentifrice. Such dentifrice compositions are capable of providing remineralization of subsurface lesions and/or mineralization of exposed dentinal tubules.
Another example is U.S. Pat. No. 6,214,321 to Lee et al. discloses a two-parts dentifrice that includes one part made of water soluble calcium phosphate salt having a pH less than 7, and a second part containing an alkaline material and a fluoride ion source to achieve a pH greater than 7.5. The two parts are stored separated and simultaneously released to generate hydroxyapatite depositing on dental enamel.
Besides dental caries, another major teeth problem facing the consumers is dental plaque build-up. Dental plaque is essentially a colorless biofilm that develops naturally on the teeth by colonizing bacteria attaching itself to a smooth surface (of a tooth). Dental plaque is soft enough to come off if scraped with a fingernail. However, If not removed, the plaque starts to harden and calcified within 48 hours, and in about 10 days the plaque becomes dental calculus (tartar), rock-hard and difficult to remove.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. In addition to being unsightly and undesirable from an aesthetic standpoint, the mature calculus deposits can be constant sources of irritation of the gingival, causing gingivitis, which if left untreated, results in periodontitis. Generally periodontitis cannot be treated by superficial use of chemotherapeutic agents, and the intervention of a dentist is required and surgery is often necessary.
A variety of methods and compositions have been described in the prior art to attempt to remove or prevent plaque and/or tartar. One example is U.S. Pat. No. 5,455,024 to Winston et al. discloses dentifrices comprised of sodium bicarbonate, zinc oxide, and an anti-caries agent to inhibit the formation of plaque
Another example is U.S. Pat. No. 6,248,310 to Lee et al. discloses a two-parts dentifrice that includes one part made of water soluble calcium phosphate salt having a pH less than 7, and a second part containing an alkaline material and a fluoride ion source to achieve a pH greater than 7.5. The two parts are stored separated and simultaneously released to generate a system for inhibiting tartar around the teeth.
While periodontitis, gingivitis, and tooth decay have longed vexed the human population, ill appearance of teeth due to stains are equally undesirable. Indeed, many individuals desire a “bright” smile and white teeth, and consider dull and stained teeth cosmetically unattractive. Unfortunately, without preventive or remedial measures, stained teeth are almost inevitable due to the absorbent nature of dental material.
Stains on teeth can be of the extrinsic or intrinsic type. The types of attractive forces involved in extrinsic dental stains include electrostatic and van der Waal forces, hydration forces, hydrophobic interactions, dipole-dipole moment forces, and hydrogen bonds. The strength of adhesion for chromogens and pre-chromogens are not well understood. A method of classification was attempted to further describe dental stains which involves three categories (Nathoo SA. The chemistry and mechanisms of extrinsic and intrinsic discoloration. J Am Dent Assoc 1997 April; 128 Suppl: 6S-10S).
In category 1 stains, the color of the discoloration is the same as the color of the material (chromogen) that causes the stain. The substances of tea, coffee and wine contain tannins and are composed of polyphenols such as catechins and leucoanthocyanins. These materials generate color due to the presence of conjugated double bonds and are thought to interact with the tooth surface via an ion exchange mechanism. Also included in the mechanism of adherence of the chromogen to the tooth is the salivary pellicle, a protein structure adhering to enamel via calcium bridges.
In category 2 stains, pigmented materials bind to the pellicle or tooth and subsequently change color. An example of this would be the cervical yellow stain turning brown with age. A proposed mechanism for this change is through the further accumulation or chemical modification of pellicle proteins (denaturation by acids or detergents). Intensification may occur via a metal bridging mechanism. Category 2 stains are considered to be more difficult to remove than category 1 stains.
In category 3 stains, the binding of a colorless material to teeth can undergo chemical reactions or transformations. The colorless material is termed a pre-chromogen. Examples of this type of staining are the induction of chlorhexidene stain, browning of foods high in carbohydrates and sugars via a rearrangement of the carbohydrates and amino acids, termed the Maillard or non-enzymatic browning reaction, and staining from stannous fluoride.
Thus, extrinsic stains result from chromogens binding either to enamel or probably more so to pellicle. The removal of a pellicle layer via a bleaching system will present a whiter tooth. The pellicle is a natural occurring biolayer and will re-establish itself if removed. It will do so with minimal chromogen build-up.
Intrinsic stains include phenomena occurring both before and after eruption of the tooth from the alveolar bone into the oral cavity. Pre-eruptive phenomena include endemic fluorosis, tetracycline staining, dentinogenesis imperfecta, and amelogenesis imperfecta. Post-eruptive phenomena include pulpal hemorrhaging, and deposition of secondary dentin or metals in a tooth from an amalgam restoration.
Everyday activities such as smoking or other oral use of tobacco products, and eating, chewing or drinking certain foods and beverages (in particular coffee, tea and red wine), cause undesirable staining of surfaces of teeth. Staining can also result from microbial activity, including that associated with dental plaque.
The chromogens or color causing substances in these materials become part of the pellicle layer and can permeate the enamel layer. Even with regular brushing and flossing, years of chromogen accumulation can impart noticeable tooth discoloration.
There are a variety of compositions described in the art for preventing or treating the discoloration of teeth. In particular, to combat staining and brighten or restore the natural enamel color, a variety of products containing bleaching materials are commercially available for professional and consumer use. The materials most commonly used in teeth whitening today are peroxides. Such peroxides include hydrogen peroxide, carbamide peroxide, sodium perborate, and sodium percarbonate.
When these peroxides are in appropriate contact with teeth they will usually oxidize the majority of stains, rendering the teeth whiter.
Current home whitening treatment methods include abrasive toothpastes, toothpastes that produce oxides, whitening gels for use with a dental tray and whitening strips.
The effectiveness of such techniques depends on a variety of factors including the type and intensity of the stain, the type of bleaching agent, contact time of the bleaching agent on the teeth, the amount of available bleaching active in the composition, the ability of the bleaching agent to penetrate the tooth enamel, and consumer compliance.
A variety of methods and compositions have been described in the prior art for whitening teeth. One example is U.S. Pat. No. 4,891,211 to Winston discloses a hydrogen peroxide-releasing toothpaste comprising sodium bicarbonate and sodium percarbonate in a polyethylene glycol base for removing stains and odor.
Another example is U.S. Pat. No. 6,521,215 to Okay discloses a dentifrice composition for whitening and remineralizing teeth, wherein the three key components are a whitening agent, a protease enzyme, and a remineralizing agent.
Another example is U.S. Application Number 2007/0071696 to Wang et al. discloses a dual phase whitening oral care composition. The composition includes a first phase that contains a whitening agent in a substantially anhydrous and orally acceptable carrier and a second phase that contains an abrasive and an anti-calculus agent in an orally acceptable carrier. The first phase and the second phase are maintained separately from each other until dispensed.
Although consumers recognize the need to maintain healthy teeth, and have used various dentifrice products on the markets for this purpose, it must be noted that majority of the consumers preferred flavored dentifrices, in particular those that provide a “refreshing” taste upon usage. Refreshing flavors such as wintergreen are known to degrade in liquid (aqueous and non-aqueous) alkaline environments. For non-liquid formulation, wet granulations often supply sufficient water to initiate the degradation process even though the ultimate product (pressed tablet, mint, or candy) appears dry. Meanwhile, other components have sufficient trapped water within their crystal structure which can be released on compression and initiate the degradation. Still other components are hygroscopic to a sufficient degree such that moisture is picked up from the ambient environment in sufficient amounts to initiate the degradation process.
Furthermore, significant wintergreen degradation is observed when the bicarbonate dentifrices are flavored with wintergreen. Bicarbonate containing dentifrice formulations are often prepared with various standard humectants such as propylene glycol, glycerin, and polyethylene glycol. Where water is present, the degradation is more pronounced than when water is absent, but even in the absence of water, wintergreen degradation is still significant with these humectants.
A variety of methods and compositions have been described in the prior art to incorporate flavors in alkaline dentifrices. One example is U.S. Pat. No. 5,709,852 to Gopalkrishnan et al., disclosing a stable non-aqueous carrier for personal care product containing flavor and bicarbonates, comprising about 80-98% by weight of anon-ionic liquid triblock EO/PO/EO copolymer of MW=1000-5000, and about 2-20% by weight of a non-ionic solid triblock EO/PO/EO copolymer of MW=4000-16,000.
However, none of the above products or references disclosing whitening and/or reminerialization addresses the issue of removing plaque build-up. Moreover, none of the references disclosing remineralization or removal/prevent of plaque teaches whitening teeth. Furthermore, some of the mentioned references teach that of a two-parts dentifrice, and none address the issue of flavor degradation in alkaline dentifrice. Given the tedious task of teeth maintenance, there is a need for developing a flavored single-part and multi-purposed dentifrice, such that it requires only a single application to achieve the functions of teeth whitening, teeth remineralization, and prevention or removal of plaque.